There's a HUGE amount of info here, as forewarned. There is also a lack of continuity in presentation, as we bounce from developers, to bleach/fix, to RA4, etc. If one's only interest (who, me?) is one shot processing in C-41, there's a lot of advice to pull out of the thread in a number of places.
Not all of us will use Kodak materials, so some of us will have to foray into alternative brands, Unicolor, Arista, Tetenol, and Compard/Rollie. But obviously that's our burden. I know that what is presented is the summation of many, many hours of work by the OP.
Here is what I'm seeing as a "cut to the chase" instructions for the C-41 part. I'm going to presume that one wants some volume of developer for one's tank, SS or plastic.:
1. Mix your developer of whatever brand to a stock solution.
2. Knowing how much developer you need for your tank, divide by 15.
3. Take that quantity of of developer and add some sodium carbonate at these ratios: For 1 liter, 3ml volume or a rounded half tsp. Of course, from there, lesser amounts or working developer, less carbonate. I know from my previous work in B&W, this isn't precision stuff. (The carbonate boost is a good catch by the OP for diluted developing.)
4. Follow advice for time/temp: 12-15 minutes with continuous or intermittent agitation at 90 degrees F, or 18 minutes at 180 degrees F, or 8 minutes at 100 degrees F.
I did like the discovery of the immateriality of bleach/fix sequence. I'll probably start doing a hard ammonium thiosulfate fix and follow with whatever blix I'm using.
Is that it? Did I miss or miscalculate anything?